The present invention is directed to a circuit arrangement for setting up conference connections in a digital time-division multiplex telecommunications switching center.
Such a circuit arrangement has a conference unit that lies in a return loop that connects the output of the voice memory that can be cyclically written into and randomly read out and that is preferably a component part of a switching network of the switching center that represents a line/trunk group for the connection of subscriber and trunk lines to the output thereof.
In such a circuit arrangement, time slots that directly follow one another and that are utilized in conjunction with the handling of conference calls (conference time slots) are additionally established on the multiplex lines connected to the input side and output side of the voice memory beyond the plurality of time slots wherein information transmissions occur from and to the switching center (transmission time slots). Corresponding to the additional time slots, conference memory cells are provided in the voice memory of the switching network and in the appertaining holding memory in addition to the voice memory cells or, respectively, holding memory cells required in the course of a switching of two-party connections. During the course of a conference call, the individual signals of the conference participants converted into conference time slots in such a circuit arrangement by random read-out from the voice memory are processed by the conference unit into final aggregate signals intended for the individual conference participants after passing through a means for linearization. These final aggregate signals do not contain the intrinsic or home part of the appertaining subscriber. After these final aggregate signals have passed through a means for companding, they return in these conference time slots to the voice memory. They are then forwarded by random read-out from the voice memory into transmission slots on the multiplex line of the output side respectively allocated to the conference participants.